1. Field of Invention
The invention relates to a method of detecting the state of the power supply, and in particular to a method of detecting and determining the phase-loss state of the three-phase power supply by means of a specific software.
2. Related Art
With the increasing popularity of power electronics, the application and utilization of power converters such as the Uninterruptible Power Supply system and the AC motor drive is widespread and is getting more and more prominent and important. For a comprehensive description of the prior in this respect, please refer to FIG. 1. FIG. 1 is a system block diagram of the ordinary DC-AC Inverter of the prior art. As shown in FIG. 1, the three-phase alternating current (AC) voltage supplied by a power source is converted to the direct current (DC) voltage through a rectifier 10, and then a filter circuit 20 is utilized to filter the rectified pulsating DC voltage into a more stable DC voltage (on the DC bus), which is then supplied to a DC-AC Inverter 30, used to generate the power supply required for the operation of a motor 50. In addition, a control circuit 40 is provided and specifically utilized to control the overall operation of the rectifier 10, the filter circuit 20, and the DC-AC Inverter 30.
When the phase-loss condition of the three-phase power source occurs, it will result in the increase of the input current of the rectifier 10, and the augmentation of the amplitude of the ripple voltage on the DC bus, thus adversely affecting the service lives of the rectifier 10 and the capacitors in the filter circuit 20. Presently, the power source phase-loss state detection and determination is done by hardware circuits. As such, it is liable to cause the additional cost of the hardware and the occupation of the additional space in the power electronics; besides, since the service life of an electronic component is of limited duration, its malfunction probability is pretty high.
Therefore, the research and development of a low cost power source phase-loss detection and determination method is an urgent and important task in this field.